Author: Kees van der Beek

Sara Bolognesi: Laureate of the Summer 2021 EPS Emmy Noether Distinction

Kees van der Beek, chair of the EPS Equal Opportunities Committee, spoke to Sara Bolognesi of CEA-IRFU in Saclay, France, laureate of the Summer 2021 EPS Emmy Noether Distinction on her work, her interactions with other communities, research funding, reconciling work and family life, and mentoring of young physicists.

Kees van der Beek (KvdB): My very warmest congratulations with the Summer 2021 Emmy Noether Distinction for your contributions to, and, indeed, leading role in the CMS and T2K experiments! Can you explain what your current scientific interests are, why your experiments are important, and what the stakes are?

Sara Bolognesi (SB): My present scientific interest is in neutrino oscillations. Neutrinos are very interesting particles, but very difficult to study! This is because they are hard to produce, and once you produced them, they are hard to detect, because of their extremely weak interaction with matter. Therefore, very large amounts of neutrinos must be produced for any given experiment, and huge detectors are needed to obtain the necessary sensibility to pronounce oneself on physical effects related to them. However, building such huge instruments is well worth it, since neutrino physics is one of the most promising avenues to push our understanding of fundamental physics beyond our present interpretation, the Standard Model. The T2K (Tokai to Kamioka) experiment seeks to quantify neutrino oscillations (evolution of one neutrino type into another) through measurement of the so-called mixing parameters. This can, given sufficient sensitivity, unveil the symmetries in the neutrino mass ordering and flavour mixing, and most importantly, a possible violation of charge-parity (CP). This would be a crucial discovery, while CP-violation has been measured in quark sector, this would be a new fundamental source of CP-violation and the first in the lepton sector. We have, so far, made significant steps towards a measurement of possible violation of CP symmetry in neutrino physics, but experiments have to be made more sensitive – which is my aim and that of my team. Remarkably, since the collisions of neutrinos with the detector material involve their complex, many-body interaction with the multiplicity of particles composing the target nuclei, reaching the required accuracy requires an adequate comprehension of the nuclear physics involved. This is true for both the accurate characterisation of the emitted neutrino flux, as for the understanding of the scattering cross-sections in the remote detector. What I love about my work is the fact that it therefore involves many different communities – every day, I learn something new!

KvdB: Is the search for new physics the reason why you made a spectacular move from Higgs physics in the framework of the CMS collaboration to neutrino physics, and this, right after the discovery of the Higgs, when results were ready for the reaping? How did you decide this shift?

SB: Indeed, after the discovery of the Higgs, the entire team was extremely excited. However, in spite of the Higgs having been discovered, there are many questions to which the standard model cannot provide answers. In particular, it cannot possibly be valid to arbitrary high-energy scales, so there must be something beyond. An illuminating overview presented by Hiroshi Murayama from Berkeley at a Higgs workshop in 2013 made it very clear to me that neutrinos are an extremely promising window to such very high-energy scales. In particular, the standard model cannot explain why neutrinos have mass, nor why they oscillate the way they do. Both these phenomena determine the numerical values of a great many parameters, so understanding them would be a particularly important step into our further comprehension of nature, and, in particular, the existence of as-yet hidden symmetries. Practically, I was greatly helped by the job opportunity formulated by CEA-IRFU, that did not only propose a permanent position, but did not require previous experience in the field of neutrino physics – indeed, they were very open to candidates form other fields. This allowed me to settle and establish myself both as a scientist and in my personal life. As a particle physicist, the learning curve in neutrino physics was steep, but I feel I was truly helped both in my institute and by the welcoming attitude of the neutrino community.

KvdB:What are the most satisfying – and more difficult parts of your work?

SB: I love the interaction between many communities and between experimentalists and theorists that characterizes neutrino physics. The most difficult part of my position is securing the necessary financial resources – we are not trained for that as physicists! Here again, I see the need to go out and obtain funding as an opportunity to learn, even if this part of the job takes up more and more of our time. We, as physicists, should accept the manner the world we live in functions. We must, before publicizing our work in physics and asking for funding, stop and really ask ourselves whether what we project to do is truly worth of funding. To have to reflect on this and then explain to non-experts why society should fund physics is an important and necessary part of our job. For me, frustration arises when decisions are made based on political priorities rather than scientific arguments. While we need a realistic compromise due to the boundary conditions posed by the world we live in, our primary goal should always be driven by physics arguments.

More fundamentally, there are better ways in which a funding process could work. Notably, the very nature of fundamental physics research requires, at the least, medium-term funding based on a vision and multi-year strategy submitted by the team, lab, institute, or collaboration submitting the request, and not the calls for short-term, individualistic projects that we see all too often today. At the same time, I’m very worried by the inertia that comes with increasing size of the collaborations and cost of the experiments. This not only slows their development but also makes it very difficult to react and adapt the overall strategy to physics evidence when new results are obtained.

I, obviously, do not hold the perfect recipe but our compass should always point to the long-term objective of advancing physics, no matter how difficult this could be from a political or funding point of view.

KvdB: You are obviously very passionate about physics, and that since a very young age. Where did you get this passion, and how did you choose physics?

SB: (laughs) You will be surprised to know that at the outset, I first started on a literary, and not on a scientific path in my secondary school studies!  It was my professor of philosophy in secondary school who suggested that we read simple texts on modern physics to open our mind. These were simple texts that addressed issues such as particle-wave duality, the nature of light, matter, and their interactions, that had a very large impact on me. I realised that this touched on something so fundamental for the understanding of our world that I could not accept to ignore it: I wanted to learn more about it! My subsequent enrolment in the physics programme at the university of Torino has lead to two life-changing experiences. The first was my participation in the CMS-Torino group as of my third year of studies, a group with several women in leadership positions.  All had a rich social and family life, as well as being highly successful physicists, which allowed me to project myself in my own possible future. The second was my work at CERN, in a truly multicultural environment. This was, to me, as much as a scientific experience, a truly human experience that made me decide that this is what I wanted for the rest of my life. In the neutrino community, which involves close collaboration between physicists from Europe, Japan, and the Americas, I find this multicultural, tolerant, and very human ambiance once again.

KvdB: Did you ever have problems reconciling your work and your family?

SB: There have been some difficult moments, but, honestly, I am working in an environment and for an employer that is extremely respectful of the balance between work and one’s private life, to the point where the balance we can achieve here is envied by our foreign collaborators. For instance, when my partner and I adopted our children, my professional environment was extremely respectful of our choice and very helpful when I returned to the laboratory. I cannot help but think that this is related to the fact that the head of my laboratory, the head of the IRFU Institute, and the head of our CEA Direction are all women. A difficult moment was the advent of the COVID-19 pandemic and the first lockdown - even if I realise that the situation was much harder for so many others. Where I had, over two years, established a good work-family life balance, this was now, all of a sudden, overturned. Here I was working from home, with three children by my side, and required to school them! The real problem here is not, in my opinion, one of gender, but that of attaining equilibrium between family life and professional life in general, whatever the family’s composition. I am very fortunate in that my husband fully participates in family tasks, including during the COVID-19 period; having a family that supports me in my professional challenges is very important for me.

KvdB: You have had many role models in Torino. Do you consider yourself to be a role model now?

SB: I hope I am! All the more so since, in my group today, there are nearly as many women as men. We do discuss gender issues as well as family issues, especially with younger women. I tell them that their life choice is, of course, theirs. However, they should never make this choice based on fear. Being afraid that one cannot be a woman and a physicist at the same time, of “not being able to”, must never be a criterion for choosing work over one’s private life or vice versa. Taking responsibility for one’s choice however comes with effort, the effort to make it work, and the effort to find one’s correct personal balance. The message I wish to convey is: if you want a career in physics, go for it, if you love physics, you will manage!

Kees van der Beek (KvdB): You are in a position of ever increasing responsibilities. Do you have ideas on how an academic, scientific environment can help empower women active in its midst?

Sara Bolognesi (SB): That’s a tough question! There are no easy solutions to this. Nevertheless, I think two things can help. The first, and most effective in my opinion, is tutoring, through examples. When one meets a young woman in doubt about her career choice, having a role model with whom she can interact or a tutor that serves as an example and build her self-confidence can really help. At T2K we also have a Diversity group that reaches out to young women in this sense. The second, and more general point is that we all, women and men, should make an effort to make our professional environment less aggressive. Even though academic discussion can be passionate, we should always be careful to respect the other, and not try to, for example, undermine the other’s self-confidence. Speak out, discuss, argue, with passion and conviction, but do so as if you were speaking to a close family member, your daughter or son, with respect and understanding. Science is an environment for discussion, where no one holds the absolute truth.

Sara Bolognesi acting on the valves of the gas system of the near detector (ND280) of T2K - image credit: Sara Bolognesi